In automobile applications, friction couplings have long been incorporated as a means to transmit or retard drive, i.e., brakes, clutches and transmissions. Rotor and stator plates are forced together and are generally encased in a dry environment so as to enhance friction characteristics. However, friction produces a great amount of heat and wear between said plates, requiring the replacement of parts and the repair of said assemblies.
A need arose to reduce the wear generated by the friction loading of the rotors and stators. As an example, wet disc friction brakes are known in the prior art. British Patent No. 651,867 and U.S. Pat. No. 3,410,375 illustrate and describe such systems. Oil, being a lubricant, tends to reduce wear associated with friction. However, the oil also reduces friction and therefore braking power. Thus increased surface area is required in order to ensure braking power in wet disc brake systems.
Wet disc brake systems have been proven to be effective and economical in many industrial and off-highway applications. However, wet disc brake systems have not enjoyed the same success in road transportation applications.
Typically, rotors and stators of a braking system are encased in a housing which is filled to capacity with oil. The oil acts to reduce wear which occurred between the mating faces of the rotors and stators, when the brakes are applied. Two factors make the design unattractive. First, high parasitic drag results from the rotors spinning in a housing full of oil which decreases fuel economy to an unacceptable level. Second, since oil is a heat capacitor, wet disc brake systems generally employ pumps and flow lines to circulate oil through the housing to transfer heat away from the rotors and stators.
Therefore, a system is needed which greatly reduces parasitic drag, has heat transfer properties thereby negating the need for pumping oil in and out of the housing. Said system must also reduce wear to the rotors and stators while sufficiently absorbing the friction and energy generated between the rotors and stators during brake application. Further, such a brake system must meet the specifications set out in Federal regulations.